U.S. Pat. No. 4,635,620--Ricchio discloses a hydro-massage bed that includes a horizontally-oriented inflatable liquid-filled cushion that includes spaced-apart nozzles through which jets of pressurized liquid or a liquid and air mixture are injected into the interior of the cushion to produce the desired massaging effect. This prior art bed is well adapted to providing the desired massage to patients while they are in a prone position, but many patients prefer to be treated while in a seated position.
To construct a chair that allows for the desired treatment of a seated patient, it is necessary to orient the inflatable liquid-filled cushion in a non-horizontal position, preferably, in an inclined position approaching the vertical. But if the cushion is so inclined and is inflated with liquid, a special problem occurs. More specifically, the cushion tends to develop a large bulge in the region that the lower back of the patient would normally rest against. This large bulge can be quite uncomfortable to the seated patient and will interfere with effective transfer of the jet action to the back of the patient. This large bulge results from the weight of the liquid in the inclined cushion and the confinement of the cushion in its lower region beneath the bulge.